Knockdown of ribosomal protein L22-like 1 arrests the cell cycle and promotes apoptosis in colorectal cancer.

Abstract

Objective: Colorectal cancer (CRC) remains a remarkable challenge despite considerable advancements in its treatment, due to its high recurrence rate, metastasis, drug resistance, and heterogeneity. Molecular targets that can effectively inhibit CRC growth must be identified to address these challenges. Therefore, we aim to reveal the regulatory effect of ribosomal protein L22-like 1 (RPL22L1) on the proliferation and apoptosis of CRC cells and its potential mechanism.

Material and methods: We detected the expression of RPL22L1 from the Cancer Genome Atlas, Gene Expression Omnibus and UALCAN databases. The effects of RPL22L1 on CRC growth and migration were determined by knocking down RPL22L1 in human CRC cell lines and those on the cell cycle and apoptosis using flow cytometry. The influence of RPL22L1 knockdown on xenograft tumor growth was verified in vivo. The potential RPL22L1 mechanisms in promoting cancer were predicted with RNA sequencing (RNAseq). The molecular mechanism of enhanced apoptosis and cell cycle arrest in RPL22L1 knockdown was revealed using real-time reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blotting.

Results: The present study reveals a considerable upregulation of RPL22L1 expression in CRC as well as in diverse tumor tissues, and most cells within the CRC tumor microenvironment (TME) demonstrate RPL22L1 expression. Notably, this elevated expression level of RPL22L1 exhibits a strong association with an unfavorable prognosis among patients diagnosed with CRC (P < 0.05). Furthermore, the association between RPL22L1 expression and the CRC TME index did not exhibit statistical significance (P > 0.05). However, RPL22L1 knockdown experiments revealed a substantial suppression of growth and migratory capacities in CRC cells RKO and HCT116 (P < 0.05). Flow cytometry analysis exhibited that on RPL22L1 knockdown, a remarkable arrest of the G1 and S phases of the cell cycle (P < 0.05) occurred. In addition, a remarkable elevation in the level of cell apoptosis was observed (P < 0.001). RNAseq exhibited that cell cycle, DNA replication, and mechanistic target of rapamycin (mTOR) complex 1pathway were inhibited after RPL22L1 knockdown, whereas the apoptosis pathway was activated (P < 0.05). Validation through RT-qPCR and western blot analysis also corroborated the downregulation of P70S6K, MCM3, MCM7, GADD45B, WEE1, and MKI67 expression levels, following RPL22L1 knockdown (P < 0.05). Consequent rescue experiments offered supportive evidence, indicating the involvement of the mTOR pathway in mediating the influence of RPL22L1 on the promotion of cell cycle progression. Moreover, in vivo assays involving tumor-bearing mice exhibited that diminished RPL22L1 levels led to arrested CRC growth (P < 0.05).

Conclusion: These findings support RPL22L1 as a possible prognostic and therapeutic target in CRC, providing novel insights into the development of anticancer medications.